1. Field of the Invention
The present invention relates to means for storing and fumigating bulk agricultural goods such as grains.
2. The Prior Art
When stored for any length of time, both raw and finished agricultural products, primarily grains, may become infested with insects and other living matter. Current fumigation techniques utilize solid and liquid chemicals convertible to gases for passage throughout the silo or other storage area. The primary liquid chemical used is methyl bromide. When mixed with air, the liquid turns into a gas which is then circulated and recirculated throughout the storage area, using expensive equipment. The liquid fumigant may be used for lightly packed raw and finished products, but in each case equipment and energy are required for circulation of the air and gas mixture, and no recirculation can occur in dense finished products such as flour.
The primary solid chemical used produces phosphine gas when exposed to air. In the case of raw agricultural products, the solid, in the form of pellets or sachets or small bags, is placed directly in the grain in the silos or storage bins. The grain must be constantly turned during the introduction of the chemical, a process which takes up to eight hours and which involves considerable trouble and expense in the physical handling of the product. Once the pellets or bags are evenly distributed throughout the grain, it requires some 72 hours for the chemical to turn into gaseous form, after which there is a powdery residue. Such residue is left in the bags whereupon the bags may be retrieved or if in pellet form, the residue may be left in the product with no ill effects.
In the case of processed or finished agricultural products, the solid chemical may not be applied directly to the grain. Governmental regulations will approve such use of phosphine gas only when the powdery residue is retained or recovered. No method is presently known or used whereby such residue can be reliably retained or recovered thereby precluding the use of solid fumigants in connection with finished agricultural products.